The invention relates to a method of improving the quality of a radio connection in a cellular radio network, comprising a base station system, a subscriber terminal and a bidirectional radio connection between the base station system and the subscriber terminal using a directional antenna beam; in which method in the base station system, an angle of incidence of the directional antenna beam is formed on the basis of a received uplink radio signal transmitted by the subscriber terminal, and the base station system transmits a radio signal on the downlink to the subscriber terminal in the direction of an angle of departure formed on the basis of the angle of incidence.
A problem presented by the arrangement described above is that it functions most properly when the radio connection between the base station system and the subscriber terminal is balanced, in other words radio signals travel regularly and symmetrically in both directions. The problem in radio connections comprising sporadic and/or asymmetrical traffic is that, because a long time may have elapsed since the reception of a previous signal from the subscriber terminal, the angle of departure does not necessarily correspond to the actual location of the subscriber terminal. During this time, the subscriber terminal may have moved too much for the signal transmitted using the angle of departure formed on the basis of the old angle of incidence to reach the subscriber terminal. The properties of the channel used in the radio connection also change on account of the change in the location. A next signal received by using an out-of-date angle of incidence and transmitted by the subscriber terminal can also be lost.
The problem is serious particularly in cellular radio networks using packet transmission; in a typical packet transmission, one party, for example the base station system, transmits much data, and the subscriber terminal possibly only transmits occasional retransmission requests. The use of a WWW (World Wide Web) browser, for example, results in heavy traffic on the downlink and light traffic on the uplink.
An object of the invention is thus to provide a method and equipment implementing the method so as to solve the above problems. This can be achieved by a method described in the introduction, which is characterized by forming a ratio for the imbalance between the downlink traffic and the uplink traffic; controlling the processing of the directional antenna beam of the radio signal on the basis of the ratio.
The invention further relates to a cellular radio network comprising a base station system, a subscriber terminal, and a bidirectional radio connection between the base station system and the subscriber terminal and using a directional antenna beam; and on the uplink, the base station system forms an angle of incidence of the directional antenna beam on the basis of a received radio signal transmitted by the subscriber terminal, and on the downlink, the base station system transmits a radio signal to the subscriber terminal in the direction of an angle of departure formed on the basis of the angle of incidence.
The cellular radio network of the invention is characterized in that the base station system is arranged to form a ratio for the imbalance between the downlink traffic and the uplink traffic, control the processing of the antenna beam of the radio signal on the basis of the ratio.
The preferred embodiments of the invention are disclosed in the dependent claims.
The invention is based on the idea that in the base station system, a ratio is formed between the amount of the traffic transmitted on the downlink and the amount of the traffic received on the uplink. By means of the ratio, problems occurring on the radio path can easily be predicted and avoided.
Several advantages can be achieved by the method and arrangement of the invention. The method enables directional antenna beams to be used in radio connections comprising sporadic and/or asymmetric traffic, particularly in packet radio systems. The method enables the most suitable algorithm for processing the directional radio beam to be selected for the situation.